With an increasing demand for higher brightness, the size of LED dies as bare chips has also been increasing, and nowadays, LED dies measuring up to 1 mm by 0.5 to 1 mm in area size are commercially available. Since this area size is about the same as that of other chip components such as resistors, there has developed a need for an LED device constructed by packaging an LED die with a resin or the like to have about the same area size as the LED die itself. Such a package is sometimes referred to as a chip size package (hereinafter abbreviated CSP) as it directly reflects the size of the LED die. A CSP has the advantage of small mounting area and a reduced amount of packaging material. It has the further advantage of being able to provide greater freedom in the design of lighting equipment, etc., because the number of components to be mounted on the mother substrate can be easily changed according to the required brightness.
FIG. 13 is a cross-sectional view of a light-emitting device 100 (LED device) implemented in CSP form according to a first prior art example.
The light-emitting device 100 shown in FIG. 13 is an ultimate form of CSP in which the chip size of the LED die is identical with the outer plan shape of the package, and this LED device is disclosed in patent document 1.
In the LED device 100, a phosphor layer 130 and a lens 132 are formed one on top of the other on the upper surface of a multilayered structure 112c (of semiconductor layers). Seed metals 122a and 122b remaining unetched when a common electrode was formed by electrolytic plating, copper wiring layers 124a and 124b, and columnar copper pillars 126a and 126b formed by electrolytic plating are located on the underside of the multilayered structure 112c. 
The multilayered structure 112c is made up of a p-type clad layer 112a, a light-emitting layer 112e, and an n-type clad layer 112b. The lower surface of the multilayered structure 112c is covered with an insulating layer 120 having openings in designated portions. Solder balls 136a and 136b are attached to the bottoms of the respective copper pillars 126a and 126b. A reinforcing resin 128 is filled into the space separating the copper pillars 126a and 126b. 
The area size of the LED device 100 shown in FIG. 13 is identical with the area size of the multilayered structure 112c. The LED device 100 is one that is diced from a wafer on which a plurality of LED devices 100 are formed in a rectangular array; such a package is the smallest one among the group of products categorized as CSPs, and is therefore sometimes referred to as a wafer-level package (WLP). In the LED device 100, since the transparent insulating substrate initially present on the multilayered structure 112c (see FIG. 2 and paragraph 0026 in patent document 1) has been removed, light emitted from the light-emitting layer 112e is allowed to emerge only in the upward direction (arrow B). Therefore, the phosphor layer 130 need only be provided on the upper surface of the LED device 100.
In the LED device 100 of FIG. 13, a laser is used to remove the transparent insulating substrate, but this requires large-scale manufacturing equipment and increases the complexity of the manufacturing process. Furthermore, since the phosphor layer 130 is formed on the LED device 100 at the wafer level, it is not possible to address variations in light emission characteristics arising among the individual LED dies produced on the wafer. This leads to the problem that it is difficult to manage the color of emission.
In view of the above problem, the present inventor experimentally produced a flip-chip LED device as an LED device that is compact in size and yet easy to manufacture and whose color of emission is easy to manage; to achieve this, the transparent insulating substrate was left unremoved, and the side faces of the transparent insulating substrate as well as the side faces of the semiconductor layer formed on the lower surface of the transparent insulating substrate were covered with a reflective resin, while the upper surface of the transparent insulating substrate and the upper ends of the reflective resin were covered with a phosphor sheet (refer to patent document 2).
FIG. 14 is a cross-sectional view of an LED device 200 according to a second prior art example. The LED device 200 shown here is disclosed in patent document 2.
The LED device 200 is constructed from an LED die 216b having a sapphire substrate 214b (transparent insulating substrate) and a semiconductor layer 215b formed on the lower surface thereof, and includes a white reflective member 217b formed on the side faces of the LED die 216b, and a phosphor sheet 211b, formed on the upper surface of the LED die 216b including the white reflective member 217b, for wavelength conversion of emitted light. An adhesive layer 213b is interposed between the phosphor sheet 211b and the sapphire substrate 214b which are thus bonded together. Protruding electrodes 218b and 219b, which are connected to the semiconductor layer 215b of the LED die 216b, are an anode and a cathode, respectively, and serve as external connecting electrodes for connecting to a mother substrate. The mother substrate is the substrate on which the LED device 200 is mounted along with other electronic components such as resistors and capacitors.
Since the phosphor sheet 211b can be selected and changed according to the light emission characteristics of the individual LED die 216b, the color of emission of the LED device 200 is easy to manage. Further, since the white reflective member 217b can serve the purpose if its thickness is reduced to 100 μm or less, the LED device 200 can be made compact in size. Furthermore, the LED device 200 is easy to manufacture, because a batch manufacturing method can be employed in which processing is performed on a large number of LED dies 216b arranged in an array on a wafer which is eventually diced into individual LED devices 200.